Process for the deoxidation and degasification of steel



Patented Apr. 8, 1941 OFFICE rnoccss eon rue DEOXIDATION ANDDEGASIFICATIONOF STEEL Paul Hardt, volklingenesaar, Germany, assignor toBiichlingsche Eisenund Stahlwerkc Gesellschaft mit bcschriinkterHaftnng, Volklingen- Saar, Germany, a limited-liability company NoDrawing. Application May 2, 1939, Serial No. 271,342. In Germany May 7,1938 2 Claims; (CL 75-57l it is a imowniact, that carbon is unsuitablefor the dcoxidation of soft steel, because small quantitles of carbonremain ineffective, whereas large quantities increase the carbon contentof the steel. ".ihe use of a carbonizing liquid consisting of tar, oil,wax, parafiin or pitch for increasing the carbon content of ingot ironor steel is also known.

it has been recognized according to the invention that, contrary to thestatements in older patent literature, hydrocarbon of high molecularweight, especially pit coal pitch, has no or only very littlecarbonizing effect but a strong deoiddiaing and degasification actionwhen added to steel baths. Pit coal pitch has been found to beparticularly effective when it is stiffened by an addition of pulverizedburnt lime dust, silicater and fluxes. It is preferably used in the formoi pressed or cast bricks.

The cause for' the deoxidizing and degaslfication effects of pit coalpitch is partly due to the evaporating pitch forming over the steel bathheavy vapors which protect the bath against contact with the air. Forexample Kilograms 1 Nm of air W ih 1.3 l Nrn coke gas weighs 0.6 1' N111anthracene vapor weighs 8.0

1700" C. anthracene vapor still has the same specific gravity as air at50 0., that is the temperature of the surroundings prevailing during thecasting. The steel is therefore always covered by a layer of pitchvapors.

Mixtures of pitch with pulverized burnt lime in a proportion of 1:3 haveshown a strong deoxidizing eifect. The lime addition may, however, bevaried. For lowering the sintering temperature of the lime, silicates.fiuor spar, soda and the. like may be added. Preferably additions areused which themselves have a purifying effect on .the steel. 0n theother hand substances such as into the liquid steel .when filling theladle or can be added in themold during the casting.

I claim: l. A process for the deoxidation and degasification of steel,consisting of treating the liquid steel with a mixture of pitch and dustof lime with the proportion of lime greater than the pitch, andsilicates and other fluxes in an amount suiiicient to lower thesintering temperature of the lime.

2. A process for the deoxidation and degasiflcation of steel, consistingof introducing a mixture in the steel bath in cold form in which themixture comprises pitch with dust of lime with the proportion of limegreater than the pitch and silicates and other fluxes in an amountsuflicien-t to lower the sintering temperature of the lime;

' PAU HARDT.

